Transformer for mercury vapor lamps



H. BUSSE TRANSFORMER FOR MERCURY VAPOR LAMPS Filed May 14, 1924 Patented June 15, 1926.

UNITED STATES 1,588,571 PATENT OFFICE.

HANS BUSSE, OF HANAU-ON-THE-MAIN, GERMANY.

TRANSFORMER FOR MERCURY VAPOR LAMPS.

Application filed May 14, 1924, Serial No. 713,301, and in Germany May 24, 1923.

Mercury vapor lamps for alternating current had, up to now in addition to the usual transformer a separate inductance coil 1nserted in the circuit of the cathode. In addition to that ,coil separate auxiliary devices for instance reversing switches, resistances etc. were indispensable for starting the are by a shortcircuit of the electrodes.

The present invention relates to improvements in transformers for such alternating current mercury vapor lamps, which allow the separate inductance coil as well as the other auxiliary devices hitherto employed to be dispensed with. v

The essential feature of the invention consists in the main core of the transformer (on which the primary coils and the secondary coils are mounted) having a supplementary core provided with an auxiliary winding, the arrangement being such that said auxiliary core is magnetized by means of the continuous current flowing through the secondary coils. The auxiliary winding of the'supplementary core is inserted in the circuit of the cathode and acts on the one hand as a secondary winding and on the other hand as a choking coil, i. e., it fulfils the same purpose up to now obtained by the separate inductance coil inserted in the circuit of the cathode. However this new arrangement has the advantage that the auxiliary winding of the supplementary core as to iron and copper only a fraction of that hitherto required for the inductance coil in the cathode circuit. Moreover, the new'arrangement chokes considerably the starting current caused by the short circuit between the main electrodes of rectifiers or alternating current mercury vapor lamps.

The connection between the supplementary core and the maincore is preferably efi'ected so that a large resistance for the magnetic flux is created. Preferably the supplementary core is connected to the main core at a point between the anode coils. The

supplementary core is subdivided, i. e. designed with a plurality of legs. The mid dle leg may for instance be connected to the main core between the anode coils and so as to create hardly any magnetic resistance. whilst the other free legs may be separated from the main core by magnetic resistances for instance air gaps. These magnetic resistances are preferably designed so that the sum of the magnetizing forces of the auxiliary winding and of the continuous current magnetism (transferred at the same time to the supplementary core from the anode coils) approximately gives the usual saturation of the iron. If desired, all the legs of the supplementary core may be connected to the main core and the required air gaps may be inserted in the legs of the supplementary core.

An alternating current mercury vapor lamp of normal construction taking a cathode current of about 4 amp. and 180 volts between the anode and cathode needs, for instance, air gaps of about 3-5 mm.

The design of the transformer herein described is especially suitable for autotransformers in which the primary coil of the main core is connected in series with the secondary coils the latter being separated from the primary coils. In this case it is important that the cross-section of the leakage path in the supplementary core be sufficiently large so that when the lamp is started by a short circuit the supplementary core takes both the whole of the primary magnetic flux and the secondary magnetic flux at the starting produced by the secondary coils of the main core (these acting as inserted choking coils).

The accompanying drawings illustrate various practical designs according to the invention.

Figures 1, 2 and 3 show three designs of the transformer for use with single phase current, Figure 1 showing the arrangement for the common connections, Figure 2 the same arrangement for an auto-transformer, whilst Figure 3 is another arrangement for auto-transformers.

Figures 4 and 5 illustrate the application of this design for multi-phase current lamps, Figure 4.- being a plan view and Figure 5, a part section along the line AB of Figure 4. The same reference letters have been used for the same parts in the various figures.

Referring to Figures 1 and 2 which are intended for single phase current lamps, the one leg 1, 2 of a core transformer 1, 2, 3, 4.- is provided with a primary or main coil 5, whilst the anode or secondary coils 6, 6 are mounted on the other leg 3, 4.

The supplementary core 8, 9, 10 is constructed with three legs and is inserted laterally into the legs of the main core carrying the anode coils in such a manner that it is connected by the middle leg 9 between the anode coils to the main core so as to present practically no resistance, whilst air gaps are provided between the legs 8 and 10 and the main core. The middle leg 9 of the core is provided with the auxiliary winding 11 which, as will be seen ,from the drawing, is inserted in the lead 12- to the cathode. 13 are the leads to the anodes, whilst in Figure 1, 14 is the conductor connecting together the secondary coils, and 15 and 16 are the feeding conductors leading "to the primary coil.

Referring to Figure 2, the secondary COllS 6, 6 and the primary coil 5 are connected so as to form an auto-transformer, that is to say the conductor connecting the secondary coils 6, 6, is dispensed with and the primary coil is connected with the secondary coils by means of the conductors 14:, the conductors 12 leading to the cathode being connected to the zero point of the primary coil. In the case of polyphase current a plurality of primary coils are employed, the conductors leading to the cathode being then connected to the zero point of all the primary coils, i. e. to the centre of symmetry of the coils. In the case of single phase current, if the single primary coil has 600 turns the zero point will be at the three-hundredth turn from which a lead is taken, which represents the zero point of the coil. It will thus be seen that the single coil may be replaced by two coils connected in series with one another and each having 300 turns. In the case of polyphase current each one of the primary coils has 300 turns, these coils being connected together at one end to a lead which thus represents the zero point of the coils.

The construction illustrated in Figure 3 differs from the construction illustrated in Figure 2 in this that no air gaps are pr0 vided between the ends of the legs 8, 10 and the main core, all the legs of the supplementary core being connected to the main core and the air gaps being inserted directly in the supplementary core.

lln the design illustrated in Figures d and 5 which is intended for three-phase current, three main secondary coils are provided and according y the supplementary core carrying the auxiliary winding is constructed with four legs, said core being connected to the leg 4 of the main core by its central leg 9 between the anode coils 6 whilst the free legs 8 of the supplementary core are separated from the main core by air gaps. The auxiliary winding mounted on the central leg and connected in the circuit of the cathode acts at the same time as a choke coil. It can be made the smaller, the greater the number of phases working together and under circumstances for instance even in the case of ordinary three-phase current may be left out altogether, provided an especially wearer uniform or smooth continuous current is not required. 5 are the primary coils which are mounted on the three lateral legs 1, 3 of the main core, said primary coils being connected with the secondary coils 6 so as to form an auto-transformer. 12 is the conductor to the cathode, 13 the leads to the anode, It the conductor connecting the primary coils 5 and the secondary coils 6 whilst 15 is the feeding conductor.

In order to obtain a transformer which shall be as noiseless as possible it has been found suitable to support. the free legs of the supplementary core against the main core in a convenient manner, and to fill the air gaps with elastic material such as vulcanized fibre etc.

The following is an example of an autotransformer Let us assume that the transformer has to feed a quartz lamp with a working of 220 volts and with a working 4.5 amp. Before the burning is started there is a noload current of about .3 amp. and when the numbers of primary and secondary turns are equal, the voltage at the terminals of the lamp amounts to 440 (corresponding to 220 volts between each anode and the oathode, the latter being in the case of an autotransformer connected to the middle point of the primary coil). lit the lamp is now started by causing a short circuit between the cathode and one or both anodes immediately after the starting, only about 80 volts are read between the anode and cathode. This is due to the fact that in the case of an auto-transformer the secondary coils, contrary to the ordinary transformer (in which the primary magnetic flux is forced on the secondary coils) form their own magnetic field, this ma etic field acting against that of the prlmary coil. lln consequence thereof, the starting current does not exceed 10 to 15 amps. whilst in the case of the old arrangement (without supplementary core and the auxiliary wind ing) the starting current would reach a \a ue whlch would be too excessive.

' In the new arrangement both the primary andthe secondary magnetic flux are atthe starting absorbed by the supplemen tary core the extent to which the two magnetic flux assist or act in opposition to one another is determined by the dimensions of the supplementary core so that the characteristic of the transformer can be essentially determined by proper design of the supplementary core.

Owing to the decrease in current by increasing the vapor pressure of the started burner, the remarkable fact may be ascertained that at about 8-9 amp. on the oathode the secondary coils entirely lose their voltage and are therefore inactive. From this time on the full supply voltage of 220 volts is to be read between the anodes of the lamp the primary coil having only to di vide this voltage into two equal parts, of 110 volts each.

As the lamp continues to burn and the current continues to decrease, the leakage in the shunt path comes more and more into operation. The pressure of the primary magnetic flux overcomes the counter pressure of the secondary flux and more and more additional voltage comes into play in the secondary coils. Finally the poles of the lamp assume a. voltage of about 360:2)(180 volts instead of 440, because also in the case of the final current of 4.5 amp. in the primary the shunt path still allows a portion of the magnetic flux to pass through, which is desirable for the proper operation of the lam since in that way a stabilizing efl'cct is o. tained as in the case of ascries resistance.

What I claim is:

1. A transformer for mercury vapor lamps comprising a main core, a primary coil mounted thereon, secondary coils mounted on the main core separatedfrom the primary coil, a supplementary core connected to the main core and a second auxiliary winding on the supplementary core serving at the same time as a choking 'coil, the supplementary core being so arranged that a magnetic flux is produced therein by a continuous current derived from the secondary coils.

2. A transformer for mercury vapor lamps comprising a main core, a primary coil mounted thereon, secondary coils mounted on the main core separated from the primary coil, a supplementary core connected to the main core and a secondary auxiliary winding on the supplementary core serving at the same time as a choking coil, said secondary auxiliary winding being inserted in the circuit of the cathode, and the supplementary core being connected to the main core between the supplementary coils so as to produce a magnetic resistance which is very small and being so arranged that a magnetic flux is produced therein by a continuous current derived from the'secondary coils.

3. A transformer for mercury vapor lamps comprising a main core, a primary winding mounted thereon, secondary windings mounted on the main core separated from the primary winding, a supplementary core lying on the outside of the main core and connected thereto and secondary auxiliary windings on the supplementary core serving as a choking coil and lying in the circuit of the cathode, the supplementary core being connected to the main core between the secondary coils so as to produce a magnetic resistance which is .very small and being so arranged that a magnetic flux is produced therein by a continuous current derived from the secondary coils.

4. A transformer for mercury vapor lamps comprising a main core, primary coils mounted on the main core, secondary windings mounted on said core separated from the primary coils, a multi-legged supplementary core, auxiliary windings mounted on the supplementary core, and serving as a choking coil and being inserted in the circuit of the cathode, the supplementary core being connected to the main core by one leg and so as to produce a magnetic resistance which is very small, the free legs being separate from the main core by magnetic resistances which are such that the magnetizing forces of the auxiliary windings together with the continuous current magnetism transferred from the secondary coils to the supplementary core and acting at the same time as the said magnetizing forces approximately give to the usual saturation of the iron.

5. A transformer for mercury vapor lamps of about 4 amp. cathode current and 180 volt pressure between the anode and cathode, comprising a main core, primary coils, mounted on the main core, secondary coils mounted on the main core and lying separate from the primary coils, a multi-legged supplementary core, auxiliary windings mounted on the supplementary core and serving also as a choking coil, such windings being inserted in the circuit of the cathode, the supplementary core being con nected to the main core by one leg so that the magnetic resistance should be very small whilst its, free legs are separated from the main core by air gaps having a width of 3-5 m. m. and in such a manner that the supplementary core is magnetized by a continuous current derived from the secondary coils.

6. A transformer for mercury vapor lamps intended to be operated with singlephase current comprising a main core, a primary coil mounted on the main core, secondary coils mounted on the said core separated from the primary coil, a threelegged supplementary core connected to the main core and secondary auxiliary windings on the supplementary core also serving as a choking coil, the said auxiliary windings being inserted in the circuit of the cathode, and the supplementary core be ing so arranged that a magnetic flux is produced therein by a continuous current derived from the secondary coils.

7. A transformer for lamps comprising a main core, a primary coil mounted on the main core, secondary windings mounted on the said core separated from the primary coil, a three-legged supplementary core connected to the main core, auxiliary windings mounted on the supplementary core and also serving as a chokmercury vapor V ing coil, the said auxiliary windings lying in lit) the circuit of the cathode, and the supplementary core being connected to the main core between the secondary coils by its middle leg and so that the magnetic resist ance should be very small, and being arranged in such a manner that a, magnetic flux is produced therein by a continuous current derived from the secondary coils.

8; A transformer for mercury vapor lamps comprising a main core, a primary coil mounted on the main core, secondary windings mounted on the said core separated from the primary coil, a three-legged supplementary core lying outside the main core,

- an auxiliary winding on the middle leg of till) dti the supplementary core also serving as a choking coil. and the supplementary core being connected to the main core by its middle leg and so that the magnetic resistance thereby produced is very small, the supplementary core being so arranged that a magnetic flux is produced therein by a continuous current derived from the secondary coils.

9. A transformer for mercury vapor lamps comprising a main core, a primary coil mounted on the main core, secondary windings mounted on the said core separated from the primary coil, a three-legged supplementary core lying outside the main core, an auxiliary winding on the middle leg of the core also serving as a choking coil, the said middle leg being connected to the main core between the secondary coils and so as to produce a magnetic resistance which is very small whilst the free legs of the supplementary core are separated from the main core by magnetic resistances which are such that the magnetizing forces of the auxiliary windings together with the continuous current magnetism transferred from the secondary coils to the supplementary core and acting at the same time as the said magnetizing forces approximately give the usual saturation of the iron.

10. A transformer for mercury vapor lamps comprising a main core, a primary coil mounted on the main core, secondary coils mounted on the said core separated from the said primary coil, a multi-legged supplementary core, an auxiliary winding on the supplementary core also serving as a choking coil, the supplementary core being connected by its legs to the main core and so as to produce a magnetic resistance which is very small, and magnetic resistances inserted in the legs of the supplementary core at suitable points with the exception of the leg carrying the auxiliary winding, the said magnetic resistances being such that the magnetizing forces of the auxiliary windings together with the continuous current magnetism transferred from the secondary coils to the supplementary ineaari core and acting at the same time as the said magnetizing torces approximately give the usual saturation of the iron.

11. A transformer for mercury vapor lamps comprising a main core, a primary coil mounted on the main core, secondary coils mounted on the said core separated from the primary coil, a multislegged supber of the main anodes, which legs are so arranged that the supplementary core is magnetized by a continuous current derived from the secondary coils.

12. A transformer for mercury vapor lamps comprising a main core, a primary coil mounted on the main core, secondary coils mounted on the said core separated from the primary coil and connected therewith .in the manner of an auto-transformer, a supplementary core attached to the main core and secondary auxiliary windings mounted on the auxiliary core and inserted in the circuit of the cathode and also serving as a choking coil, the supplementary core being so arranged that a magnetic tlux is produced therein by a continuous current derived from the secondary coils.

13. A transformer for mercury vapor lamps, comprising a main core, a primary cell mounted on the main core, secondary coils mounted on the said core separated from the primary coil and connected therewith in the manner of an auto-transformer, a three-legged supplementary core lying outside the main core, an auxiliary winding mounted on the middle leg of the supplementary core, said winding being in serted in the circuit, of the cathode and serving also as a choking coil, said su plementary core being connected to t e main core between the anode coils and so as to produce a magnetic resistance; which is very small, whilst the free legs of the supplementary core are separated from the main core by magnetic resistances which are such that the magnetizing forces of the auxiliary windings. together with the continuous current magnetism transferred from the secondary coils tov the supplementary core and acting at the same time as the said magnetizing forces approximately give the usual saturation of the iron. i

14. A transformer for fimcrcury vapor lamps comprising a main core, a primary coil mounted on the main core, secondary coils mounted on the said core se arated from the primary coil and-connecte therewith in the nicer of an auto-transformer,

a supplementary core connected to the main core, an auxiliary winding on the supplementary core serving also as'a choking coil,

the supplementary core being so arranged that it is magnetized by .a continuous current derived from the secondary coils and the section of the leakage path in the supplementary core being sufiiciently large that when the lamp is started by a short circuit it does not absorb only the whole of the primary magnetic flux but in addition thereto also the secondary magnetic flux which is produced at the starting by the secondary coils on the main core acting in this case as choking coils.

15. A transformer for mercury vapor lamps comprising a main core, a primary coil mounted on the said core separated from the rimary coil and connected therewith in t e form of an auto-transformer, a three-legged supplementary core lying outside the main core and an auxiliary winding on the middle leg of the supplementary core lying in the circuit of the cathode and also serving as a choking coil, the supplementary core being connected to the main core between the secondary coils and so as to produce a magnetic resistance which is very small, and magnetic resistances between. the free legs of the supplementary core and the main core, the said free legs being so arranged that the supplementary core is magnetized by a continuous current derived from the secondary coils, the section of the leakage path being made sufiiciently large that when the lamp is started by a short circuit not only the whole of the primary magnetic flux but also the secondary magnetic flux is absorbed by it, which secondary magnetic flux is roduced at the starting by the secondary 001 s of the main core WhlCh act as choking coils.

" In testimony whereof I aflix my signa- HANS BUSSE. 

